1. Field of the Invention
Embodiments relate to a thin film transistor, a flat panel display device having the same, and associated methods.
2. Description of the Related Art
In general, a thin film transistor (“TFT”) includes a semiconductor layer and a gate electrode. The semiconductor layer includes a channel region, a source region, and a drain region. The gate electrode corresponds to the channel region of the semiconductor layer and is electrically insulated therefrom. The semiconductor layer may be formed of amorphous silicon or polysilicon. When the semiconductor layer is formed of amorphous silicon, the mobility may be low. Accordingly, it may be difficult to employ such TFT's in high speed circuits. In contrast, polysilicon may provide high mobility. The threshold voltage of TFT's formed from polysilicon may be non-uniform, however, and thus an additional compensating circuit may be required. Moreover, manufacturing a TFT using low temperature polysilicon (LTPS) may require expensive processes such as laser annealing, and it may be difficult to control operational characteristics for large area substrates.
In view of the difficulties in advancing amorphous silicon and polysilicon TFT technologies, research into the use of compound semiconductors has been increasing. In particular, compound semiconductors formed of zinc oxide (ZnO), or including zinc oxide in combination with other materials, e.g., dopants, have been of interest. However, TFT's including compound semiconductors may exhibit relatively high resistivities, e.g., 1×104 to 1×106 Ω·cm. Accordingly, there may be a high contact resistance where metal electrodes contact source and drain regions formed from the compound semiconductor. Implanting hydrogen (H) atoms into the compound semiconductor may reduce the resistivity the semiconductor layer and reduce the contact resistance, but hydrogen in the channel region may increase leakage current.